Recently, with the active development of electric vehicles, storage batteries, robots, satellites, and the like, along with the dramatically increasing demand for portable electronic products such as laptop computers, video cameras, mobile phones, and the like, research and development for high-performance secondary batteries capable of repeatedly charging and discharging has been actively made.
Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a cathode active material and anode active material, respectively. The lithium secondary battery includes an electrode assembly in which a cathode plate and an anode plate respectively coated with the cathode active material and the anode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can type secondary battery where the electrode assembly is included in a metal can and a pouch type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Generally, the performance of a secondary battery may deteriorate due to a temperature, and if a temperature rises, a secondary battery may be heated or exploded. Further, since the secondary battery includes various combustible substances therein, the heating or explosion of the secondary battery may cause another external component to be fired or exploded, which may result in damage of property or human life. In addition, if a temperature of a secondary battery rises to deform a shape of a component such as a separator, the secondary battery may be fired or exploded due to an internal short circuit of a cathode and an anode.
In this circumstance, in order to ensure safety according to a temperature of a secondary battery, a current interruption module for restricting a current according to a temperature of the secondary battery, for example a temperature cut-out (TCO) or a positive temperature coefficient (PTC), is generally used.
FIG. 1 is a schematic view showing a general battery pack in which a pouch-type secondary battery 10 is connected to a current interruption module, and FIG. 2 is a schematic view showing that a protection circuit module 30 is connected to the battery pack of FIG. 1.
In most cases, a secondary battery 10, particularly a pouch-type secondary battery 10, does not include a current interruption module 20 such as a TCO, which responds to a temperature. Therefore, the current interruption module 20 such as a TCO is generally connected to an outside of the pouch-type secondary battery 10.
In addition, the general pouch-type secondary battery 10 is connected to a protection circuit module (PCM) 30 which controls charging or discharging to prevent the secondary battery 10 from being overcharged or overdischarged. However, in this case, the pouch-type secondary battery 10 and the protection circuit module 30 are not directly connected, but the current interruption module 20 such as a TCO is generally interposed between them.
For this, in an existing technique, as shown in FIG. 1, an electrode tab 11, for example a cathode tab, of the pouch-type secondary battery 10 is firstly welded to one end of the current interruption module 20. In addition, the cathode tab welded to the current interruption module 20 as described above is bent toward the pouch-type secondary battery 10, as indicated by the arrow a in FIG. 2, and placed on a terrace T of the secondary battery 10. By doing so, the current interruption module 20 is located closest to the secondary battery 10, which allows the temperature of the secondary battery 10 to be sensed more accurately and thus the resultant current interruption ability to be enhanced.
After that, the other end of the current interruption module 20 is connected to a contact portion 31 formed at the protection circuit module 30. At this time, various components for controlling charging or discharging of the secondary battery 10 may be mounted to the protection circuit module 30, and an external connection terminal 32 connected to an external component to input or output a charging/discharging current of the secondary battery 10 may be provided.
However, in the above configuration, the current interruption module 20 should be independently attached to each of a plurality of secondary batteries 10, which results in complicated production processes and increase of costs. In particular, this problem may be worse in a middle- or large-sized battery pack including many secondary batteries 10 in a single battery pack.
In addition, in a general battery pack configured as above, after the electrode tab 11 and the current interruption module 20 are welded, the current interruption module 20 may damage a pouch of the secondary battery 10 while the electrode tab 11 is bent and the current interruption module 20 is placed on the terrace T of the secondary battery 10. Moreover, in an existing battery pack, to ensure insulation against the current interruption module 20, an insulation tape is frequently attached to the terrace T of the secondary battery 10, which however may increase production time and costs.